#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <assert.h>

char* my_strcat(char* dest, const char* src)
{
    char* ret = dest;
    assert(dest != NULL);
    assert(src != NULL); 
    while (*dest)
    {
        dest++;
    }
    while (*src)
    {
        *dest = *src;
        dest++;
        src++;
    }
    *dest = '\0'; 
    return ret;
}

int main()
{
    char arr1[100] = "arr1";
    char arr2[] = "arr2";
    my_strcat(arr1, arr2);
    printf("%s", arr1);
    return 0;
}